FIG. 1A shows a prior art operational transconductance amplifier (OTA) 10 according to the prior art. The prior art OTA 10 receives a positive-side input voltage VP at a non-inverting input to the prior art OTA 10. Further, the prior art OTA 10 receives a negative-side input voltage VN at an inverting input to the prior art OTA 10. The prior art OTA 10 provides an output current IO based on a voltage difference between the positive-side input voltage VP and the negative-side input voltage VN. Specifically, the voltage difference is equal to a magnitude of the positive-side input voltage VP minus a magnitude of the negative-side input voltage VN. In this regard, since the prior art OTA 10 provides the output current IO based on the voltage difference, the prior art OTA 10 functions as a transconductance amplifier. As such, a transconductance GM of the prior art OTA 10 is equal to a magnitude of the output current IO divided by the voltage difference. Additionally, the prior art OTA 10 receives a first DC source signal DC1 and a second DC source signal DC2 to provide power to the prior art OTA 10.
FIG. 1B shows the prior art OTA 10 and a prior art OTA load circuit 12 according to the prior art. The prior art OTA load circuit 12 is coupled between an output from the prior art OTA 10 and a ground. The prior art OTA load circuit 12 has a load impedance ZL. The prior art OTA load circuit 12 receives the output current IO, such that an output voltage VO from the prior art OTA 10 is developed across the prior art OTA load circuit 12. In this regard, a magnitude of the output voltage VO is equal to the magnitude of the output current IO times a magnitude of the load impedance ZL. Since the prior art OTA 10 is an operational amplifier, the prior art OTA 10 may have very high input impedances and an open-circuit transconductance of the prior art OTA 10 may be very high. Therefore, the prior art OTA 10 may combine the functionality of an operational amplifier with transconductance characteristics, which may be useful in certain applications.